Piezo-electric-crystal apparatus



Oct. 23, 192s. 1,688,714

A. HUND PIEZO ELECTRIC CRYSTAL APPARATUS Filed May 12, '1927 llll INVENTOR.

A NOR/JY Pau-,med oct. 23, 192s.

UNITED STATES PATENT OFFICE.

AUGUST HUND, OF BETHESDA, MARYLAND, ASSIGNOR 'IO WIRED RADIO, INC., OF NEW YORK, N. Y., A CORPORATIONIOF DELAWARE.

D PIEZO-ELECTRIC-CRYSTAL APPARATUS.

. Application iiled May 12,

My invention relates broadly to piezo electric crystal apparatus and more particularly to a holder for piezo electric crystal elements arranged for the production of constant frequency currents.

One of the objects of my invention is to provide a holder for piezo electric crystal elements which are arranged for the production of audible frequency currents with means for adjusting the frequency within a limited range for accurately setting the edsctive frequency of the apparatus.

Another object of my invention is to provide a piezo electric crystal apparatus having a plurality of piezo electric crystal elements in close association therein, with means for independently establishing connection with said piezo electric crystal elements and accurately adjusting the eective frequency of the piezo electric crystal apparatus for control of electrical circuits.

Still another object of my invention resides in the construction and arrangement of parts of a piezo electric crystal holder as described in the following specification and illustrated in the accompanying drawing in which:

Figure 1 is a cross-sectional view taken through the piezo electriccrystal apparatus of my invention; Figure 2 is a cross-sectional viewtaken through the piezo electric crystal apparatus on line 2-2 of Fig. 1; Fig. 3 is a cross-sectional view taken through the apparatus on line 3-3 qf Fig. 1; Fig. 4 shows the application of my invention to va multiple piezo electric crystal holder where plates, I have shown that comparatively small piezo electric crystal elements may be used for the production of audio frequency currents. Low frequency currents may be produced by means of a single element with a step formed in the element, or an element cut at an angle with respect to the optical axis, or a multiplicity of piezo electric crys- 1927. Serial No. 190,881.

tal elements which individually vibrate at a high rate of frequency differing from each other by a beat frequencymay be used for *integrating the effects of the several freand the cooperating surfaceof the piezo electric crystal element for the selective setting of the gap between the electrode and the surface of the piezo electric crystal element to -that size which will give the desired frequency in an associated work circuit.

Referring to the drawings in detail reference character 1 designates a conductive plate member upon which the insulated housing 2 is positioned by means of the screw members 3 which pass through the plate 1 and are screw threaded into the insulated housing 2. Insulated housing 2 is provided with a central bore having a plurality of differing cross-sections. The lower portion of the bore is provided with an enlarged cross-section indicated at 4. The cross-section is then reduced. as represented at 5, and again enlarged as shown at 6 and internally screw threaded for receiving a retaining member 7 providing a bearing for the rotatable shaft 8 with its enlarged shoulder 9 thereon. The rotatable shaft 8 has a tubular portion 10 thereon which is internally screw threaded as indicated at 11 for receiving the screw threaded stub member 13 which carries the electrode 14 on the end thereof. The electrode 14 maybe shifted vertically with respect to the upper surface ofthe piezo electric crystal element 40. Rotation of the electrode 14 is prevented by means of pin 15, whichis arranged to slide within the pocket 16. The piezo electric crystal element 20 has its lower `surface in contact with the conductive plate 1. The

adjustment of the electrode" 14 permitsl of j work-circuit from the piezo electric crystal apparatus. The piezo electric crystal ele ment 20 is provided With a step or is cut at such an angle that current of a frequency within the audible range may be generated and the integral effects of the currents generated by the different portions of the piezo electric crystal elements utilized in a circuit system which may be connected with the piezo electric crystal apparatus. f

In Fig. 4 I have shown separate piezo electric crystal elements designated at 21'and 22 to which electrical connection can be made by means of this adjustable device illustrated in Fig. 1. The piezo electric crystal elements 21 and 22 are selected with a frequency dierence equal to a beat frequency whose alternating current is Within the audible range. I have shown an adjustable device for establishing connect-ion with the upper Surface of piezo electric crystal element 22 which is similar to the construction of the device which establishes connection with the upper surface of piezo electric crystal element 21 and constructed in accordance with the structure illustrated in Fig. 1. Similar parts of the apparatus have been designated at 4', 5', 6', 7', 8', 9', 10', 11', 12', 18', 14', 15 and 16'. v

In Fig. 5 I have shown a construction of holder for piezo electric crystal elements which cooperate to produce a relatively low frequency beat note wherein the piezo electric crystal elements 21 and 22 are mounted upon metallic plate members 28 and 24 which are positioned within recesses 23a and 24a in the insulated base member 25 and electrically connected one with the other by means of a wire member 26 Which may pass through the base 25. The piezo electric crystal elements 21 and 22 are segregated from each other by means of an insulated spacer member 27 which is secured upon the insulated base'member 25 by screw members 28 which pass through the metallic plate 29 which forms the upper contact for the top surfaces of the piezo electric crystal elements 21 and 22. The gap which is provided between the upper face of the piezo electric crystals andthe lowerside surface of the conductive plate 29 is of the order of .2 to .3 mm., or is of such a size as may be selected for vmaintaining the desired control .frequencyin the circuits associated with the piezo electric' crystal apparatus.

In the piezo electric crystal apparatus where provision is made for the adjustment of the gap it will be noted that in each instance rotation of the upper .electrode is prevented permitting an extremely accurate setting of the gap by a movement toward or away from theupper surface of the piezo electric crystal.

The adjustable feature of the piezo electric crystal apparatus is extremely desirable for causing a slight change or shift in the beat frequency and a change in the audio frequency tone.

In the claims I have used the expression thickness axis and by this I refer to an imaginary line which extends perpendicularly to the upper and lower surfaces of the piezo electric element. The adjustable member in the crystal holder is aligned centrally with respect to the thickness axis of the crystal holder.

The piezo electric crystal of my invention has been found to be extremelyy practical in construction and efficient in its operation, and while I have described my invention in preferred embodiments, I desire it to be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

Vhat I claim as new and desire to secure by Letters Patent of the United States is as follows:

l. Piezo electric crystal apparatus comprising a metallic plate member, an insulated housing carried by said metallic plate member, and having pockets formed therein for receiving piezo electric crystal elements mounted in position upon said plate member and adjustable electrodes carried by said housing centrally of each of the pockets therein for establishing an electrostatic connection with the surfaces of said piezo electric crystal elements.

2. Piezo electric crystal apparatus comprising a metallic plate member, piezo electric crystal elements positioned upon said metallic plate member for electrically connecting the lowerv surfaces of said piezo electric crystal elements, an insulated housing carried by said plate member, adjustable electrodes positioned in said insulated housing over the upper surfaces of each of said piezo electric crystal elements, said electrodes being independently adjustable With respect to the upper surfaces of said piezo electric crystal elements for selectively adjusting the effective control frequency of said piezo electric crystal elements.

3. Piezo electric crystal apparatus comprising a connecting plate member, a multiplicity of piezo electric crystal elements having their lower surfaces in contact with said connecting plate member, an insulated housing carried by said plate member, and having pockets formed therein for centering each of said piezo electric crystal elements with respect to said plate member, and an adjustable electrode projecting through said insulated housing and into each of the pockets formed therein for establishing electrical connection with the upper surfaces of each of said piezo electric crystal elements.

4. Piezo electric crystal-apparatus comprising a conductive base member, an inlUU sulated housing 'carried by said base member, and having a pocket formed therein, a piezo electric crystal element having its lower surface resting incontact with said conductive base member, a rotatable sleeve member journaled in said housingand having its axis centrally aligned with the thickness axis of said piezo electric crystal element., ,an electrode substantially conforming to the -shape of the upper surface of said piezo electric crystal element, and a screw threaded shank extending from the rear of said electrode and engaging said rotatable sleeve member whereby said electrode may be advanced or retracted with respect to the upper surface of said piezo electric crystal element.

5. Piezg electric cr stal apparatus comprising a. conductive base member, a piezo electric crystal element having its lower surface resting in contact with said conductive base member, an insulated housing carried by said base member, and `having' a pocket formed therein for receivin said piezo electric crystal element, a rotata le member journaled in said housing and having its vertical axis coincident with the thickness axis of said piezo electric crystal element, said rotatable member being internally screw threaded, an electrode substantially conforming with the shape of the lupper surface `of the piezo electric crystal element, a screw threaded shank extending from the rear of said electrode and engaging the internally screw threaded rotatable member, means extending between said electrode and said housing for preventing rotary movement of said electrode while permitting the advancing or retracting thereof for adjusting the gap between said electrode and the upper surfaceI of said piezo electric cystal element.

In testimony whereof I aiiix my signature.

' AUGUST HUND. 

